Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 112 for “"anechoic"”.
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Anechoic chamber design and acoustical analysis of room 1-051
Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1987.
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Aerodynamics and Acoustics of the Virginia Tech Stability Tunnel Anechoic System
The acoustic treatment and calibration of a new anechoic system for the Virginia Tech Stability Wind Tunnel has been performed. This novel design utilizes Kevlar cloth to provide a stable flow boundary, which eliminates the need for a free jet and jet catcher. To test this concept a series of …
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Finite element-boundary elements modelling of acoustic scattering from viscoelastic anechoic structures
… work focuses on the analysis of multi-layered, anechoic tiles for underwater applications, especially in the field of communications. It is firstly shown how the sound absorbing properties of viscoelastic materials can be modified and enhanced by the proper use of fillers, such as lead oxide and …
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The Design, Fabrication, and Evaluation of a Low-Speed, Low-Turbulence, Anechoic Wind Tunnel
… and fans, a low-speed, low-turbulence, anechoic wind tunnel was designed, fabricated and evaluated at Embry-Riddle Aeronautical University.</p> <p>This open circuit wind tunnel was designed using several other existing wind tunnels as a guide and incorporated an open jet test section. …
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Retrieval of Free Space Radiation Patterns through Measured Data in a Non-Anechoic Environment
… measurements are usually carried out in an anechoic chamber. However, a good anechoic chamber is very expensive to construct. Previous research has attempted to compensate for the effects of extraneous fields measured in a non-anechoic environment to obtain a free space pattern that would be …
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Aeroacoustic Study of a Model-Scale Landing Gear in a Semi-Anechoic Wind Tunnel
… 777 main landing gear in the Virginia Tech (VT) Anechoic Stability Wind Tunnel. The VT Anechoic Stability Wind Tunnel allowed noise measurements to be carried out using both a 63-elements microphone phased array and a linear array of 15 microphones. The noise sources were identified from the …
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Design of anechoic chamber instrumentation and data acquisition module for testing and analysis of the CTHA
… against electromagnetic radiation, called anechoic chambers. The objective of this work is to design and build an automated data acquisition system to map the field of physically small antennas such as a Contrawound Toroidal Helical Antenna (CTHA), placed inside an anechoic chamber built …
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Effects of anechoic vs. reverberant sound-field, subject gender, and outlier dismissal on the real-ear attenuation of hearing protection devices
… a diffuse sound field was established within an anechoic chamber (free-field), as permitted by ANSI S12.6-1984 "Method for the Measurement of the Real-Ear Attenuation of Hearing Protectors" using four loudspeakers, one at each vertex of a tetrahedron with the subject's head center position at the …
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Characterizing The Acoustic Properties Of The Jet Lab At The National Center For Physical Acoustics
… to jet noise must be researched and addressed. Anechoic chambers were proposed as a testing facility for research in aerodynamic noise because of their supposed free-field characteristics. The international standard ISO 3745-1977 was introduced to determine whether the facilities could be …
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Design and Verification of a LabVIEW Automated Antenna Radiation Pattern Measurement System
… Toyon Research Corporation donated a 6’x6’x8’ anechoic chamber to the Cal Poly EE department to advance student education in the areas of antennas and wireless communications. An anechoic chamber is a room designed to suppress electromagnetic radiation reflections so that accurate measurement …
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Structure-Property Evaluation of the Dielectric Properties of Radar Absorbing Materials in Free Space
… dielectric properties. The use of Free Space and anechoic chamber instrumentation are two such ways to achieve information on samples that are lossy, i.e. materials that have the ability to quickly dissipate EM radiation. For this work, several commercial polymer matrices were used with 4 …
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A measurement study of 802.11n links on commodity hardware
… at diff erent times of day, and in an anechoic chamber. We find that 802.11n, which uses MIMO, presents a peculiar nature of performance in indoor and anechoic chamber environments and presents some interesting challenges as well as opportunities for better rate control algorithm design.
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Experimental design to determine the effect of temperature and Mach number on entropy noise
… In the test rig, compressed air enters an anechoic labyrinth, flows through a settling chamber that straightens airflow, and then goes to the entropy wave generator. The entropy wave generator forms entropy waves through electric heating. Entropy waves are then accelerated in a …
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A Calibration Method for a Controlled Reception Pattern Antenna and Software Defined Radio Configuration
… CRPA and SDR system was characterized in an anechoic chamber environment to closely replicate the fielded antenna/receiver system. This combined CRPA and SDR system calibration method configuration can provide multi-antenna element characterization and calibration measurements that can be …
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Null subtraction imaging technique for biomedical ultrasound imaging
… to assess lateral resolution and cylindrical anechoic and hyperechoic targets to assess contrast. A 9L4 array was used in the measurements connected to an Ultrasonix RP system with a SonixDAQ. Image reconstruction involved using delay and sum beamforming with apodization. Images were …
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Studies on the role of the mammalian external ear in directional hearing
… using pure tones and broadband sound under anechoic conditions.
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Measurement and Prediction of Rotor Noise Sources for sUAS in Outdoor and Laboratory Environments
… available eVTOL rotors in an enclosed anechoic environment and an open environment. For experimental measurements that were conducted in the anechoic chamber, recirculation effects were shown to increase harmonic amplitudes more than 8 dB. Varying solidity screens were placed in the …
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The Control of Interior Cabin Noise Due to a Turbulent Boundary Layer Noise Excitation Using Smart Foam Elements
… represented by an experimental test panel in an anechoic box mounted to the side of a wind tunnel. The rig was used to simulate turbulent boundary layer noise transmission into and aircraft cabin. An active noise control (ANC) methodology was employed by covering the test panel with the smart …
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An investigation of drone propeller noise generation in a turbulent wake
… wind tunnel at UNSW. The facility consists of an anechoic chamber attached to a closed return, hardwalled aerodynamic tunnel via a Kevlar window to permit noise measurements. This setup is used to characterize propeller noise in both the streamwise and planarwise orientation. The effect of …
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Prediction of sound pressure and intensity fields in rooms and near surfaces by ray tracing
… or more surfaces made of these materials, in an anechoic chamber, a scale-model room, and a full-scale office space. Prediction accuracy in the anechoic chamber, and in the presence of a single reflecting surface, greatly improved with the inclusion of phase. Further comparison with full-scale …
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